The relationships between five culture factors (glucose, ammonium ion, chitin, scleroglucan, and initial inoculum concentration) and the production of N-acetylhexosaminidase, endochitinase, and beta-1,3-glucanase enzymatic activities by Trichoderma atroviride strain PI were studied using response surface modeling. Experiments were performed using a 5-factor, 3-level, central composite face-centered design. Enzyme activity levels were modeled using partial least-squares regression (PLS). Enzyme activity levels were strongly affected by both glucose concentration and pH. When the enzyme activity levels were modeled over a range of four factors that excluded wide changes in pH, the most influential factors were chitin and inoculum. The highest production of all three enzyme activities was predicted at glucose concentrations between 0.01 and 0.1%, ammonium ion between 18 and 25 mM, and chitin, scleroglucan, and initial inoculum, at the highest levels tested (0.8, 0.2 and 1 x 10(7) conidia/50 ml starter culture, respectively). (c) 2005 Elsevier Inc. All rights reserved.